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    SubjectRe: [Bad page] trying to free locked page? (Re: [PATCH][RFC] fix kernel BUG at mm/migrate.c:719! in 2.6.26-rc5-mm3)
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    On Tue, 2008-06-17 at 18:15 +0900, Daisuke Nishimura wrote:
    > On Tue, 17 Jun 2008 18:03:14 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
    > > On Tue, 17 Jun 2008 16:47:09 +0900
    > > Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
    > >
    > > > On Tue, 17 Jun 2008 16:35:01 +0900, Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
    > > > > Hi.
    > > > >
    > > > > I got this bug while migrating pages only a few times
    > > > > via memory_migrate of cpuset.
    > > > >
    > > > > Unfortunately, even if this patch is applied,
    > > > > I got bad_page problem after hundreds times of page migration
    > > > > (I'll report it in another mail).
    > > > > But I believe something like this patch is needed anyway.
    > > > >
    > > >
    > > > I got bad_page after hundreds times of page migration.
    > > > It seems that a locked page is being freed.

    I'm seeing *mlocked* pages [PG_mlocked] being freed now with my stress
    load, with just the "if(!page->mapping) { } clause removed, as proposed
    in your rfc patch in previous mail. Need to investigate this...

    I'm not seeing *locked* pages [PG_lock], tho'. From your stack trace,
    it appears that migrate_page() left locked pages on the list of pages to
    be putback. The pages get locked and unlocked in unmap_and_move(). I
    haven't found a path [yet] where the page can be returned still locked.
    I think I need to duplicate the problem.

    > > >
    > > Good catch, and I think your investigation in the last e-mail was correct.
    > > I'd like to dig this...but it seems some kind of big fix is necessary.
    > > Did this happen under page-migraion by cpuset-task-move test ?
    > >
    > Yes.
    >
    > I made 2 cpuset directories, run some processes in each cpusets,
    > and run a script like below infinitely to move tasks and migrate pages.

    What processes/tests do you run in each cpuset?

    >
    > ---
    > #!/bin/bash
    >
    > G1=$1
    > G2=$2
    >
    > move_task()
    > {
    > for pid in $1
    > do
    > echo $pid >$2/tasks 2>/dev/null
    > done
    > }
    >
    > G1_TASK=`cat ${G1}/tasks`
    > G2_TASK=`cat ${G2}/tasks`
    >
    > move_task "${G1_TASK}" ${G2} &
    > move_task "${G2_TASK}" ${G1} &
    >
    > wait
    > ---
    >
    > I got this bad_page after running this script for about 600 times.
    >





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